Urine storage and voiding are important roles of the lower urinary tract and regulated by a coordinated action of the bladder and the urethra. That is, during urine storage, the bladder smooth muscle is relaxed while the urethral smooth muscle and the external urethral sphincter are contracted, whereby a state of high urethral resistance is maintained, and urinary continence is maintained. On the other hand, during voiding, the bladder smooth muscle is contracted, the urethral smooth muscle is relaxed, and the contraction of the external urethral sphincter is also suppressed. Examples of dysfunctions in the lower urinary tract include urine storage dysfunctions such as overactive bladder in which urine cannot be retained during urine storage, and voiding dysfunctions in which urine cannot be drained sufficiently during voiding due to an increase in the urethral resistance or a decrease in the contractile force of the bladder. In some cases, these two dysfunctions simultaneously develop.
Voiding dysfunctions are caused by an increase in the urethral resistance or a decrease in the bladder contractile force during voiding, and lead to voiding difficulty, straining during voiding, attenuation of the urinary stream, extension of voiding time, an increase in residual urine, a decrease in voiding efficiency, or the like. As a cause of an increase in the urethral resistance, a voiding dysfunction accompanied by benign prostatic hyperplasia is well-known, which is characterized by partial obstruction of the urethra due to nodular hypertrophy of the prostate tissues. Currently, adrenergic α1 receptor antagonists are being used as therapeutic drugs for the voiding dysfunction associated with benign prostatic hyperplasia (Pharmacology, 65, 119-128 (2002)). An increase in the urethral resistance is also caused by functional obstruction in detrusor-external urethral sphincter dyssynergia or the like resulting from neurological diseases or neurological disorders. In patients with these diseases, the effectiveness of adrenergic α1 receptor antagonists is unclear (Journal of Pharmacological Sciences, 112, 121-127 (2010)).
Meanwhile, as a factor for decreasing the contractile force of the bladder during voiding, aging, diabetes, benign prostatic hyperplasia, neurological diseases such as Parkinson's disease and multiple sclerosis, spinal cord injury, nerve damage caused by pelvic surgery, and the like are known (Reviews in Urology, 15, 11-22 (2013)). As therapeutic drugs for a decrease in the bladder contractile force during voiding, bethanechol chloride which is a non-selective muscarinic receptor agonist and distigmine bromide which is a cholinesterase inhibitor are known. However, these drugs are known to have cholinergic side effects such as diarrhea, abdominal pain, sweating, and the like. Furthermore, cholinergic crisis is expressed as a serious side effect in some cases, and accordingly, caution is required in using the drugs (UBRETID (registered trademark) tablet 5 mg package insert, Torii Pharmaceutical Co., Ltd., Besacolin (registered trademark) powder 5% package insert, Eisai Co., Ltd.).
In voiding dysfunctions caused by an increase in the urethral resistance or a decrease in the bladder contractile force as described above, residual urine after voiding may be observed in some cases. Increased residual urine may cause a decrease in effective bladder capacity, and this leads to overactive bladder symptoms such as urinary frequency, or severe symptoms such as hydronephrosis in some cases. Therefore, there is a demand for a therapeutic drug which is more effective on bladder and/or urinary tract diseases or symptoms thereof caused by an increase in the urethral resistance during voiding or a decrease in the bladder contractile force (Reviews in Urology, 15, 11-22 (2013)).
Melanocortins are peptides generated by the processing from proopiomelanocortin, and examples thereof include an adrenocorticotropic hormone, and α-, β-, and γ-melanocyte stimulating hormones (α-, β-, and γ-MSH). Hitherto, five subtypes (MC1 to MC5) of melanocortin receptor (MC receptor) have been reported. Any of the subtypes belongs to a G protein-coupled receptor of a class A, and activates an adenylate cyclase via the Gs protein so as to increase the amount of cAMPs. The MC4 receptors are widely distributed in the central nervous system, and are known to play an important role in feeding behavior, energy metabolism regulation, sexual function, and the like (Folia Pharmacologica Japonica, 128, 53-55 (2006)).
As representative MC4 receptor agonists, the following compounds have been reported.
It is described that a compound represented by the formula (A) has an MC4 receptor agonistic action and is useful for treating and/or preventing diseases relating to the activation of the MC4 receptor, such as obesity, diabetes, and sexual dysfunction (in particular, erectile dysfunction). (Patent Document 1)

(In the formula, R1 represents a C1-10 alkyl group which may be substituted with R3 or the like, R2 represents phenyl which may be substituted with R3 or the like, X represents C1-8 alkyl which may be substituted with R3 or the like, and m represents 0 or the like. See Patent Document 1 for other symbols.)
It is described that some compounds including the compounds of the following formulae (B) and (C) have a binding activity with respect to a human MC4 receptor. (Non-Patent Document 1)

It is described that a compound represented by the formula (D) has an MC4 receptor agonist action and is useful for treating and/or preventing diseases relating to the activation of the MC4 receptor, such as obesity, diabetes, and sexual dysfunction (in particular, erectile dysfunction). (Patent Document 2)

(In the formula, R1 represents a C1-8 alkyl group which may be substituted with R3 or the like, and R2 represents phenyl which may be substituted with R9 or the like. See Patent Document 2 for other symbols.)
It is described that a compound represented by the formula (E) can be used as a ligand of a melanocortin receptor, for treating diseases such as feeding disorder, obesity, inflammation, pain, chronic pain, skin disorder, skin and hair pigmentation, sexual dysfunction, dry eyes, acne, anxiety neurosis, depression, Cushing's disease, and the like. (Patent Document 3)

(In the formula, A represents C5-7 cycloalkyl, aryl, or heteroaryl, X1 and X3 represent CR5R6 or the like, X2 represents NR8, and R3 represents aryl which may be substituted. See Patent Document 3 for other symbols.)
It is described that some compounds including the compounds of the following formulae (F) and (G) have a binding activity with respect to a human MC4 receptor. (Non-Patent Document 2)
